I. Field of the Invention
The present invention relates to wireless telecommunications. More particularly, the present invention relates to a method and apparatus for utilizing the polarization of signals to facilitate the transmission and reception of signals processed using code division multiple access (CDMA) signals.
II. Description of the Related Art
The IS-95 standard (IS-95) defines a Code Division Multiple Access (CDMA) over-the-air interface for providing efficient and robust cellular telephone service. The IS-95 standard has been approved by the Telecommunication Industry Association (TIA) to allow cellular telephones and base stations manufactured by different suppliers to interoperate with one another. An illustration of a cellular telephone system configured in accordance with the use of the IS-95 standard is provided in FIG. 1. Also, a cellular telephone system configured substantially in accordance with the use of IS-95 is described in U.S. Pat. No. 5,103,459 entitled "System and Method for Generating Signal Waveforms in a CDMA Cellular Telephone System" assigned to the assignee of the present invention and incorporated herein by reference.
CDMA signal processing allows a set of user signals to be transmitted over the same radio frequency (RF) band by modulation of the user signals with a set of pseudorandom noise codes (PN codes) before up conversion to an RF frequency band. The PN codes are used to modulate and demodulate the user signals during transmission and reception processing respectively. The primary benefit of using CDMA signal processing is that adjacent base stations can use the same RF bandwidth to conduct communications, which increases the frequency reuse factor, and therefore the efficiency, with which the cellular telephone system uses the available RF bandwidth.
Another benefit of CDMA technology is that it allows multipath signal processing. Multipath signal processing is the individual processing of different copies of the same transmitted signal that are created by reflection and other multipath phenomenon. Typically, the various copies of the transmitted signal are processed by a set of demodulators, each synchronized with the state of the PN codes for that signal. During the processing of a particular multipath signal, the other unsynchronized multipath signal are detected as background noise or interference. Once each multipath signal is processed, the resulting "soft decision" data is typically combined into a single data set, and the single data set decoded.
While the use of multipath signal processing improves the performance of a CDMA receive processing system, the interference generated by the other multipath signals during the processing of a particular multipath signal is still undesirable. This interference can result in fading, and reduce the total number of communications that can be conducted by a particular base station. If a method and apparatus for reducing the degree to which the set multipath signals interfere with one another could be provided, the performance of multipath receive processing system could be improved still further. It is to this end, as well as other ends discussed below, that the present invention is directed.